Ubisoft games are only not on Steam UK, thus making me think this has to do with price, its well known people in the UK get games on steam cheaper than the EU and USA, Ubi not happy about this I think.

I'm guessing this is a reaction to Vavle dropping various Ubisoft games from Steam because of the 'always connected' DRM. I assume that SC:C was going to use it and now they've changed their mind because Valve have made a stand.